my guess is, because all app’s are supposed to be web built, is that it’s all going through the net, does the app warn you that you will be sending text or anything in that direction ?
No, I’m almost certain it is using your 3G or Wireless internet connection, not the SMS services, so you’ll only be charged for your data use on the 3G internet, which I expect will be little considering that you are only sending text which isn’t a very large piece of information to send.
The only thing that uses text and SMS is the SMS feature on the iphone, everything else is EDGE/3G data plan use based, meaning they run off of your data plan.